Production Of Copolymers Research Articles

Regulating copolymer architecture using photoiniferter polymerization to direct composite morphology

Due to mild conditions and straightforward synthetic routes, photoiniferter polymerization has received increasing use as a facile method for preparation of polymers with highly controlled structure. However, low quantum yields inherent to thiocarbonylthio species result in polymerization speeds that are considerably slower than traditional controlled radical polymerization techniques. To improve polymerization speed while maintaining high level control, it is critical to understand relationships between reaction parameters and ultimate polymer structure. In this work, initiating light intensity, reactant concentration, and monomer pendant groups were manipulated in the photoiniferter polymerization of acrylate monomers to explore the effect of these conditions on reaction kinetics and molecular weight control. Polymerization rate of n-butyl acrylate was significantly enhanced by increasing light intensity rivaling speeds of conventional thermally initiated RAFT polymerization while enabling more precise control over molecular weight. Interestingly, photoiniferter rate asymptotically approached saturation at relatively high light intensities. Moreover, degradation of trithiocarbonate species occurred at greater intensities, ultimately resulting in moderate increases in molecular weight. Increased reactant concentration enabled faster rates with bulk polymerization, possibly due to reduced macro radical mobility and termination. Additionally, comparing photoiniferter polymerization of methyl acrylate and hydroxyethyl acrylate showed that greater polarity considerably enhanced polymerization speeds. Finally, the utility of precisely controlling polymer structure was demonstrated by synthesizing and incorporating a series of amphiphilic block copolymers with increasing molecular weight into a photocurable epoxy resin. The well-defined block copolymer structures enabled controllable phase separation and thermomechanical properties in epoxy composites. This work showed that photoiniferter polymerization speeds could be significantly enhanced using elementary reaction conditions, and that these conditions enable facile production of well-defined copolymers allowing tailored composite morphology and properties.

Production of PHA copolymers consisting of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx) by recombinant Halomonas bluephagenesis

Microbial synthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), namely PHBHHx, with different 3HHx monomer ratios have shown biocompatibility, biodegradability and flexibility for commercial uses. This study aims at the low-cost production of PHBHHx with customized and/or rich 3HHx by engineered Halomonas bluephagenesis (H. bluephagenesis), which is a rising-star chassis for Next Generation Industrial Biotechnology (NGIB). Recombinant H. bluephagenesis harboring heterologous PHA synthase (PhaCac) and enoyl coenzyme-A hydratase (PhaJac) could produce PHBHHx from glucose and sodium hexanoate. After rationally fine-tuning the expression levels of phaCac and phaJac employing two inducible promoters, Plac and Plux induced by IPTG and AHL, respectively, the resulting H. bluephagenesis TDC-CJ produced 55 wt% P(3HB-co-14.21 mol% 3HHx). Furthermore, two inducible promoters were replaced by constitutive ones, Pporin68 and Pporin58, respectively, with similar expression strength to remove the additions of inducers. Notably, PHBHHx of high 3HHx ratios, reaching up to 49 mol%, was further obtained by weakening the native β-oxidation pathway. Finally, chromosomally engineered H. bluephagenesis G34 with two expression cassettes of phaCJ on loci G3 and G4 was constructed to achieve the synthesis of P(3HB-co-36 mol% 3HHx) without supplementing antibiotic. For lab-scale fermentation in a 7-L bioreactor, H. bluephagenesis G34 produced PHBHHx with controllable molar fraction of 3HHx from 0-to-37 mol% by designing glucose/hexanoate ratio. These efforts demonstrate that engineering H. bluephagenesis is of great potential for PHBHHx production of low cost for industrial-scale biomanufacturing purpose.

Cascading Beta-oxidation Intermediates for the Polyhydroxyalkanoate Copolymer Biosynthesis by Metabolic Flux using Co-substrates and Inhibitors

ABSTRACTPolyhydroxyalkanoates (PHAs) are biopolymers that are produced within the microbial cells in the presence of excess carbon and nutrient limitation. Different strategies have been studied to increase the quality and quantity of this biopolymer which in turn can be utilized as biodegradable polymers replacing conventional petrochemical plastics. In the present study, Bacillus endophyticus, a gram-positive PHA-producing bacterium, was cultivated in the presence of fatty acids along with beta-oxidation inhibitor acrylic acid. A novel approach for incorporating different hydroxyacyl groups provided using fatty acids as co-substrate and beta-oxidation inhibitors to direct the intermediates to co-polymer synthesis was experimented. It was observed that higher fatty acids and inhibitors had a greater influence on PHA production. The addition of acrylic acid along with propionic acid had a positive impact, giving 56.49% of PHA along with sucrose which was 1.2-fold more than the control devoid of fatty acids and inhibitors. Along with the copolymer production, the possible PHA pathway functional leading to the copolymer biosynthesis was hypothetically interpreted in this study. The obtained PHA was analyzed by FTIR and 1H NMR to confirm the copolymer production, which indicated the presence of poly3hydroxybutyrate-co-hydroxyvalerate (PHB-co-PHV), poly3hydroxybutyrate-co-hydroxyhexanoate (PHB-co-PHx).

Antioxidants Role Against Acrylamide Toxicity on Urogenital System: An Overview

Acrylamide (AA) is a chemical substance which is used as a soil stabilizing agent and in the production of copolymers and polymers since 1970. The presence of an AA adduct in food was observed in rats fed with fried food which led to a substantial increase in levels of hemoglobin adduct. Foods that are rich in carbohydrate when prepared at high temperature (above 120 ºC) by baking, toasting, frying, roasting or cooking results in the production of AA by the reaction of the amino acid with glucose present in it. Several studies observed AA toxicity on nervous system, reproductive system, and immune system. To justify this toxicity there is not a clear mechanism described. In this review article the mechanisms of AA toxicity on urogenital system and role of antioxidants against its toxicity has been reviewed. According to previous studies the main factor that induces AA toxicity is oxidative stress. AA treated groups revealed degeneration of the kidney’s epithelial lining and the glomerular tuft. Adverse effect on reproductive system by AA has been evidenced by sperm-head abnormalities, dominant lethal effects, and testicular epithelial tissue degeneration. Therefore, it is advised that modifying of food processing methods and consuming lot of vegetables and fruits containing antioxidants. These antioxidants give us some supports to the cells of our body organs against the AA sources which cause cell defects.

Construction of membrane reactors coupled with conjugated network hollow microspheres for cascade production of block copolymers

We present a design for cascade polymer production by exploiting the construction of membrane reactors coupling with conjugated network hollow microspheres as suspended catalysts to combine aqueous photopolymerization and membrane separation process.

Highly efficient and well-controlled ROP and copolymerization of cyclic esters using a cesium complex.

A cesium imino-phosphanamidinate, [{NHIDippP(Ph)NDipp}Cs], enabling efficient ring-opening (co)polymerization of rac-LA and ε-CL is disclosed. Owing to the highly controlled polymerization, precise di-block copolymers (PLA-b-PCL) with different block lengths can be produced by a simple one-pot reaction. NMR, GPC, DSC and microscopic analyses confirm the production of di-block copolymers with crystalline properties.

Study of maleic anhydride based water treatment agents

The research results of maleic anhydride water treatment agents in the past years were summarized and analyzed, which provided reference for further research and preparation of environmental protection water treatment agents. A binary copolymer product with excellent scale inhibition and dispersion properties was synthesised using maleic anhydride and sodium allyl sulfonate as monomers. The product was characterized and its properties were investigated. It was concluded that the product has excellent scale inhibition and dispersion performance and good biodegradability. The product is an environmentally friendly water treatment agent.

Measurement and Modeling of Semi-Batch Solution Radical Copolymerization of N-tert-Butyl Acrylamide with Methyl Acrylate in Ethanol/Water.

The synthetic polymer industry is transitioning from the use of organic solvents to aqueous media in order to reduce environmental impact. However, with radical polymerization kinetics affected by hydrogen-bonding solvents, there is limited information regarding the use of water as a solvent for sparingly soluble monomers. Thus, in this paper, the radical polymerization of methyl acrylate (MA) and N-tert-butylacrylamide (t-BuAAm) is studied in water and ethanol (EtOH), as the copolymer product is of commercial interest. A series of semi-batch reactions are conducted under a range of operating conditions (i.e., reaction temperature, solvent-to-monomer ratio, and comonomer composition) to demonstrate that the copolymer can be successfully synthesized without significant drifts in product molar masses or composition. The experiments provide additional data to probe the influence of the solvent on the polymerization rate and copolymer properties, as the low monomer concentration maintained under starved-feed operation leads to a solvent-to-monomer ratio different from that in a batch system. A model that captures the influence of backbiting and solvent effects on rate, previously developed and tested against batch polymerizations, also provides an excellent description of semi-batch operation, validating the set of mechanisms and kinetic coefficients developed to represent the system.

CFD modeling of the ethylene–vinyl acetate copolymerization autoclave reactor: Effects of comonomer ratio on reactor dynamics and copolymer properties

Computational fluid dynamics (CFD) modeling of an industrial ethylene–vinyl acetate autoclave copolymerization reactor was conducted to evaluate the effects of comonomer ratios on reactor dynamics and product properties, including the molecular weight distribution (MWD), and copolymer composition. To accurately predict the MWD of copolymer chains under highly nonideal mixing conditions at a reduced computational cost, the CFD-multicompartment model and probability generating function (PGF) transform were applied. The effectiveness of the developed model was validated by the satisfactorily consistent plant data and simulated results. The model revealed that an increase in the vinyl acetate (VA) content significantly decreased the temperature, promoting combinational termination and chain transfer to polymer reaction for a broad copolymer MWD. The pseudo-kinetic-based analysis showed that VA was consumed more slowly than ethylene, resulting in its lower value in the copolymer composition than that of the comonomer ratios. However, despite nonideal mixing, the copolymer composition was maintained to be uniform for the copolymers produced over the entire reactor volume. In conclusion, the proposed model can be used to understand the governing behaviors of copolymerization under nonideal mixing conditions, design commercial copolymerization reactors, and predict copolymer product qualities.

Polyhydroxyalkanoate Production from Fruit and Vegetable Waste Processing.

Traditional plastics represent a tremendous threat to the environment because of increases in polluting manufacturing as well as their very extended degradation time. Polyhydroxyalkanoates (PHAs) are polymers with similar performance to plastic but are compostable and synthesizable from renewable sources and therefore could be a replacement for fossil-based plastics. However, their production costs are still too high, thus demanding the investigation of new and cheap substrates. In this sense, agricultural wastes are attractive because they are inexpensive and largely available. Specifically, fruit and vegetables are rich in sugars that could be fermented into PHAs. In this work two strains, Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034, well-known PHA-producing microbes, were screened for their ability to grow and accumulate PHAs. Ten different fruit and vegetable processing waste streams, never before reported in combination with these strains, were tested. Residues from red apple and melon were found to be the most suitable feedstocks for PHA production. Under specific selected conditions, C. necator DSM 545 accumulated up to 7.4 and 4.3 g/L of 3-hydroxybutyrate (3HB) from red apple and melon, respectively. Copolymer production was also obtained from melon. These results confirm the attractiveness of food processing waste as a promising candidate for PHA production. Ultimately, these novel substrates draw attention for future studies on process optimization and upscaling with C. necator.

Highly Efficient Production of Nanoporous Block Copolymers with Arbitrary Structural Characteristics for Advanced Membranes.

The great significance of boosting the design of percolating nanopore structures in block copolymers (BCPs) for various cases has been widely demonstrated in the past several decades. However, it still remains challenging to prepare the desired porous structures in a rapid, facile, and universal manner. Here we have developed an unconventional and benchtop strategy to rapidly generate the nanoporous polystyrene-based BCPs with arbitrary structural characteristics regardless of the BCP bulk morphology. This universal pore-forming strategy enables the sustainable CO2 -based BCPs to form advanced membranes after 1 s soaking for efficiently rejecting 94.2 % brilliant blue R (826 g mol-1 ). Meanwhile, the water permeance retains around 1020 L (m2 h bar)-1 , which is 1-3 orders of magnitude higher than that of other membranes. This strategy may offer an excellent opportunity to introduce percolating pore structures in those newly developed BCPs with which the previously reported pore-forming methods may not deal.

Highly Efficient Production of Nanoporous Block Copolymers with Arbitrary Structural Characteristics for Advanced Membranes

AbstractThe great significance of boosting the design of percolating nanopore structures in block copolymers (BCPs) for various cases has been widely demonstrated in the past several decades. However, it still remains challenging to prepare the desired porous structures in a rapid, facile, and universal manner. Here we have developed an unconventional and benchtop strategy to rapidly generate the nanoporous polystyrene‐based BCPs with arbitrary structural characteristics regardless of the BCP bulk morphology. This universal pore‐forming strategy enables the sustainable CO2‐based BCPs to form advanced membranes after 1 s soaking for efficiently rejecting 94.2 % brilliant blue R (826 g mol−1). Meanwhile, the water permeance retains around 1020 L (m2 h bar)−1, which is 1–3 orders of magnitude higher than that of other membranes. This strategy may offer an excellent opportunity to introduce percolating pore structures in those newly developed BCPs with which the previously reported pore‐forming methods may not deal.

Unsterile production of a polyhydroxyalkanoate copolymer by Halomonas cupida J9

Microbial production of bioplastics polyhydroxyalkanoates (PHA) has opened new avenues to resolve “white pollution” caused by petroleum-based plastics. PHAs consisting of short- and medium-chain-length monomers, designated as SCL-co-MCL PHAs, exhibit much better thermal and mechanical properties than PHA homopolymers. In this study, a halophilic bacterium Halomonas cupida J9 was isolated from highly saline wastewater and proven to produce SCL-co-MCL PHA consisting of 3-hydroxybutyrate (3HB) and 3-hydroxydodecanoate (3HDD) from glucose and glycerol. Whole-genome sequencing and functional annotation suggest that H. cupida J9 may possess three putative PHA biosynthesis pathways and a class I PHA synthase (PhaCJ9). Interestingly, the purified His6-tagged PhaCJ9 from E. coli BL21 (DE3) showed polymerizing activity towards 3HDD-CoA and a phaCJ9-deficient mutant was unable to produce PHA, which indicated that a low-substrate-specificity PhaCJ9 was exclusively responsible for PHA polymerization in H. cupida J9. Docking simulation demonstrated higher binding affinity between 3HB-CoA and PhaCJ9 and identified the key residues involved in hydrogen bonds formation between 3-hydroxyacyl-CoA and PhaCJ9. Furthermore, His489 was identified by site-specific mutagenesis as the key residue for the interaction of 3HDD-CoA with PhaCJ9. Finally, PHA was produced by H. cupida J9 from glucose and glycerol in shake flasks and a 5-L fermentor under unsterile conditions. The open fermentation mode makes this strain a promising candidate for low-cost production of SCL-co-MCL PHAs. Especially, the low-specificity PhaCJ9 has great potential to be engineered for an enlarged substrate range to synthesize tailor-made novel SCL-co-MCL PHAs.

Tailoring Polymer-Based Nanoassemblies for Stimuli-Responsive Theranostic Applications.

Polymer assemblies on the nanoscale represent a powerful toolbox for the design of theranostic systems when combined with both therapeutic compounds and diagnostic reporting ones. Here, recent advances in the design of theranostic systems for various diseases, containing-in their architecture-either polymers or polymer assemblies as one of the building blocks are presented. This review encompasses the general principles of polymer self-assembly, from the production of adequate copolymers up to supramolecular assemblies with theranostic functionality. Such polymer nanoassemblies can be further tailored through the incorporation of inorganic nanoparticles to endow them with multifunctional therapeutic and/or diagnostic features. Systems that change their architecture or properties in the presence of stimuli are selected, as responsivity to changes in the environment is a key factor for enhancing efficiency. Such theranostic systems are based on the intrinsic properties of copolymers or one of the other components. In addition, systems with a more complex architecture, such as multicompartments, are presented. Selected systems indicate the advantages of such theranostic approaches and provide a basis for further developments in the field.

One-pot production of a graft copolymer of cationic starch and cationic polyacrylamide applicable as flocculant for wastewater treatment

A newly developed, high-performance, and environmentally friendly flocculant, i.e., a graft copolymer of cationic starch and cationic polyacrylamide (SC-CPAM), is synthesized via a single-step pathway in which the cationic agent is incorporated onto the starch backbone and into the polyacrylamide grafted branch simultaneously. One-pot preparation method is quick, reproducible, and easily scalable, which yields high-quality products with better flocculation performance than conventional cationic starch (SC) and starch-graft-polyacrylamide (S-PAM). The synthesized samples are characterized by physicochemical techniques, namely Fourier Transform Infrared Spectroscopy (FTIR), elemental analysis, H1 Nuclear Magnetic Resonance (H1NMR) Spectroscopy, Zeta Potential (ZP), and Dynamic light scattering (DLS). The application as a flocculant for wastewater treatment is investigated by flocculation of kaolinite suspension and analysis of turbidity (UV-Vis and NTU), ZP, and floc size in neutral pH. A high clarification of 97.8%, low turbidity of 1.97 NTU, and large floc size of 136 µm, obtained by SC-CPAM, are believed to result from dual flocculation mechanisms, i.e., polymer charge patch and particle bridging, enabled by the cationic high molecular weight branched bio-based flocculant for wastewater purification applications.

Polymers Based on PLA from Synthesis Using D,L-Lactic Acid (or Racemic Lactide) and Some Biomedical Applications: A Short Review.

Poly(lactic acid) (PLA) is an important polymer that is based on renewable biomass resources. Because of environmental issues, more renewable sources for polymers synthesis have been sought for industrial purposes. In this sense, cheaper monomers should be used to facilitate better utilization of less valuable chemicals and therefore granting more sustainable processes. Some points are raised about the need to study the total degradability of any PLA, which may require specific composting conditions (e.g., temperature, type of microorganism, adequate humidity and aerobic environment). Polymerization processes to produce PLA are presented with an emphasis on D,L-lactic acid (or rac-lactide) as the reactant monomer. The syntheses involving homogeneous and heterogeneous catalytic processes to produce poly(D,L-Lactic acid) (PDLLA) are also addressed. Additionally, the production of blends, copolymers, and composites with PDLLA are also presented exemplifying different preparation methods. Some general applications of these materials mostly dedicated to the biomedical area over the last 10–15 years will be pointed out.

Switchable Polymerization Organocatalysis: From Monomer Mixtures to Block Copolymers.

One-pot production of sequence-controlled block copolymer from mixed monomers is a crucial but rarely reached goal. Using a switchable Lewis-pair organocatalyst, we have accomplished sequence-selective polymerization from a mixture of O-carboxyanhydride (OCA) and epoxide. Polymerization of the OCA monomer occurs first and exclusively because of its exceedingly high polymerizability. When OCA is fully consumed, alternating copolymerization of epoxide and CO2 liberated in OCA polymerization is triggered from the termini of the first block. The two polymerizations thus occur in tandem, both in chemoselective fashion, so that a sequence-controlled block polymer with up to 99 % CO2 conversion is furnished in this one-pot protocol. Calculations and experimental results demonstrate a chemoselective and cooperative mechanism, where the high polymerizability of the OCA monomers guarantees exquisite sequence selectivity and the cooperative decarboxylation partly arose from the stabilization effect by triethylborane, which facilitates the smooth transformation of the chain end from carbonate to alkoxide.

Minimal mechanism for cyclic templating of length-controlled copolymers under isothermal conditions.

The production of sequence-specific copolymers using copolymer templates is fundamental to the synthesis of complex biological molecules and is a promising framework for the synthesis of synthetic chemical complexes. Unlike the superficially similar process of self-assembly, however, the development of synthetic systems that implement templated copying of copolymers under constant environmental conditions has been challenging. The main difficulty has been overcoming product inhibition or the tendency of products to adhere strongly to their templates-an effect that gets exponentially stronger with the template length. We develop coarse-grained models of copolymerization on a finite-length template and analyze them through stochastic simulation. We use these models first to demonstrate that product inhibition prevents reliable template copying and then ask how this problem can be overcome to achieve cyclic production of polymer copies of the right length and sequence in an autonomous and chemically driven context. We find that a simple addition to the model is sufficient to generate far longer polymer products that initially form on, and then separate from, the template. In this approach, some of the free energy of polymerization is diverted into disrupting copy-template bonds behind the leading edge of the growing copy copolymer. By additionally weakening the final copy-template bond at the end of the template, the model predicts that reliable copying with a high yield of full-length, sequence-matched products is possible over large ranges of parameter space, opening the way to the engineering of synthetic copying systems that operate autonomously.

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

INFLUENCE OF ADDITIONAL INHIBITORS ON CATALYTIC DESTRUCTION REACTION OF POLYISOBUTYLENE

It is impossible to create a scientific basis for the synthesis of polymers without taking into account the destruction process. Under the action of Lewis acids, the destruction of PIB follows a free radical chain mechanism, while the catalytic destruction of PIB leads to the formation of both linear and branched macromolecules. The most wide-spread type of chemical destruction is an oxidative destruction by oxygen and ozone. The oxidative destruction is activated by heat, light rays and mechanical energy, and the types of thermal, photo and mechanical oxidative destruction are known, respectively. As a result of these destructive reactions, both the composition and the structure of polymer change, that is, it “grows old”. The aging of a polymer means a change in its physical-chemical, physical-mechanical properties during exploitation . The fastest oxidative destruction of polymers occurs by a chain mechanism (with free radicals), as in low molecular weight hydrocarbons. The oxidation process of polymers without double bonds in the chains proceeds weakly, and the formation of peroxide groups is not always observed in them. This process consists of three stages: formation of an active center, lengthening and breaking of the chain. It is known that oxidation begins with the formation of peroxides. Active centers are obtained by the decomposition of peroxides. When studying the chemistry of the reaction, it was noticed that there is another mechanism for the destruction of polyisobutylene in the presence of strong Lewis acids, characteristic of cationic processes. One of the interesting aspects of the destruction process is a complete understanding of the "chemistry" of catalytic destruction. For this, various additives must be added to the catalytic reaction. During the experiments it has been found that the reaction does not take place in a completely dried solvent. The reaction proceeds when a significant amount of water is added to the system. The amount of water in the system is [H2O] ≈10-3 mol / l. This can be explained by the fact that the catalyst in dimer form is inactive in the nonpolar helix, but the water plays the role of a polar additive, decomposing the dimer catalyst and converting it into the monomeric form of Brønsted acid. Therefore, the inhibitory effect of 2,6-DTBP and toluene on the reaction has been studied in order to fully elucidate the chemistry of the catalytic destruction of PIB by Lewis acids. Since 2,6-DTBP is a trap for protons, it plays an important role in the detection of the active form of the catalyst. The ineffectiveness of 2,6-DTBP and toluene as an inhibitor led to the existence of a radical reaction mechanism and the discovery of the active form of the catalyst. For better understanding the reaction mechanism, the inhibitory effect of O2, p-benzoquinone and tetracyanethylene on the reverse process has been studied. The formation of block copolymers upon modification of PIB with acrylonitrile and vinyl acetate, polymerized by the radical mechanism, not only confirms the radical mechanism of destruction, but also creates conditions for the production of new copolymers. The formation of active centers has been also confirmed by the EPR method, free macroradicals have been detected and their density has been determined. The formation of free macroradicals as a result of the direct action of strong mechanical energy, direct mechanical cracking or transfer of vibration energy of the initial highly active state of the polymer chain is the initial stage of mechanical and chemical processes. The overall final result of the transformations depends on the direction of the subsequent secondary reactions of free macroradicals. Although these reactions are different, they correspond to typical free radical processes in polymer systems. On the whole, destructive reactions are considered one of the most important reactions for high molecular weight compounds. They are used to study the structure of high molecular weight compounds, as well as to obtain low molecular weight compounds from the natural polymers. All this has been reflected in IR, UV, NMR, EPR spectroscopic studies. A mathematical and kinetic model of the processes has been developed and parameters have been calculated using the experimental indicators of the carried out researches. Keywords: catalyst, 2,6-DTBP, toluene, polyisobutylene, destruction, halide, aikyl halide, inhibitor, deactivation, methano